One of the most reliable deep-sea explorers may have plunged too far down in the ocean and has apparently been lost.

According to BBC News, the Nereus, a robotic vehicle managed by the Woods Hole Oceanographic Institution (WHOI), apparently crumbled under the pressure of the water. It was investigating the Kermadec Trench northeast of New Zealand about six miles underwater when it apparently imploded.

The WHOI found debris that appears to have come from the vehicle on the surface of the water where it was performing its latest mission.

"To obtain some kinds of knowledge - particularly when physical samples are required for analysis - there is no alternative to sending equipment into the deep ocean, because the ocean's watery veil masks its depths from many forms of 'remote sensing,'" Jonathan Copley, a British oceanographer at the University of Southampton, wrote in a blog post this weekend. "And although we have learned a lot from a century or so of largely 'blind sampling' by equipment such as trawls and seabed corers (which are still fine for answering some questions in some areas), we now often require more detailed sampling and surveying, using deep-sea vehicles, to answer further questions."

Based in Woods Hole, Mass., WHOI built Nereus in 2008 for approximately four-and-a-half million dollars. The vehicle was remote controlled but also had a mode where it could act on its own.

"Extreme exploration of this kind is never without risk, and the unfortunate loss of Nereus only underscores the difficulty of working at such immense depths and pressures," WHOI Director of Research Larry Madi said in a press release. "Fortunately there was no human injury as a consequence of this loss. WHOI scientists and engineers will continue to design, construct and operate even more advanced vehicles to explore and understand the most remote and extreme depths of our global ocean."

Nereus was 30 days into a mission set to last 40 days. The mission was the first of its kind, a systematic study of a deep-ocean trench.

"Nereus helped us explore places we've never seen before and ask questions we never thought to ask," Timothy Shank, project chief scientist, said in the release. "It was a one-of-a-kind vehicle that even during its brief life, brought us amazing insights into the unexplored deep ocean, addressing some of the most fundamental scientific problems of our time about life on Earth."